SANTA CLARA, Calif. (AP) — 49ers coordinator Robert Saleh viewed the game against the Cowboys in October as the low point for his defense.

San Francisco allowed 265 yards rushing, far and away the most this season.

It was an affront to Saleh's core defensive philosophy: Stop the run first.

"The Dallas game still punches me in the stomach, punches all of us really," Saleh said.

But the team has shown stark improvement in six games since. San Francisco's defense is allowing an average of 106 yards on the ground and 3.63 yards per carry. Last season, the 49ers allowed 4.8 yards per rush and 166 per game.

For Saleh, who said 4.0 yards per carry is the benchmark for his defense, that improvement begins with the mindset he instilled when he first began working with his players last spring.

"Obviously, if you can stop the run, you can get after the passer," Saleh said.

"To try to get teams to be one-dimensional. So the first thing you do in the scheme is to stop the run. Everything is designed to stop the run. Since I've been blessed to be a part of the scheme however many years ago, we've always had a very successful run defense."

The 49ers defense is up for a different type of challenge Sunday against the Titans, who feature a dynamic rushing attack with DeMarco Murray and 2015 Heisman Trophy winner Derrick Henry.

"They have a large, probably the biggest run-game playbook I've ever seen on tape," Saleh said. "They come at you many different ways."

The Titans are second in the NFL with 17 rushing touchdowns. Murray and Henry have split carries and combined for 1,201 yards. They both have five rushing scores, matching quarterback Marcus Mariota, who's also a prominent piece of the versatile attack.

Mariota suffered a knee sprain in Sunday's loss to the Cardinals but has been a full participant in practice this week. Standout left tackle Taylor Lewan returned to practice Thursday after missing Wednesday's session with a back injury.

The Titans (8-5) have lost two of four while Mariota has struggled with turnovers throughout the season. He's thrown 10 touchdowns and 14 interceptions, dampening the high expectations surrounding Tennessee entering the season.

Mariota's top target is tight end Delanie Walker, who provides the offense a versatile downfield threat to balance the 10th-ranked running game.

"He's a beast and I'm excited for the challenge," 49ers safety Eric Reid said of Walker. "He's probably one of the better receiving tight ends that I've faced this year, if not the best. ... He's their go-to guy. So I know when I'm covering him, just to expect the ball to be coming."

NOTES: 49ers RT Trent Brown (shoulder) missed practice on Thursday for the second straight day. ... DT DeForest Buckner and DT Earl Mitchell were given the day off. ... TE George Kittle is back on the injury report this week while dealing with a lingering ankle injury that caused him to miss the win over the Giants on Nov. 12.

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